CubeRRT: CubeSat Radiometer RFI Technology Validation Mission Joel T. Johnson, Chi-Chih Chen, C. Ball, A. O’Brien, L. Garry, M. Andrews, C. McKelvey, G. Smith The Ohio State University Sid Misra, Shannon Brown, Jonathan Kocz, Bob Jarnot NASA JPL Jeffrey Piepmeier, Jared Lucey, Priscilla Mohammed, Damon Bradley, K. Horgan, M. Solly NASA GSFC NASA Earth Science Technology Forum 15 June 2016
RFI Problem for Microwave Radiometry • Microwave radiometers are important Earth Observing systems for a variety of science applications (land, ocean, atmosphere, …) • Observe the naturally generated microwave thermal emission from Earth – Man-made transmissions cause radio-frequency interference (RFI) GMI Images at 10.7 (left) and 18.7 (right) GHz showing RFI ‘hot spots’ Radiometers avoid RFI (ideally) by operating in frequency bands where transmission is prohibited • SMAP 1% of measurements have RFI > 30K, 10% have RFI > 3K (in a protected band!) 2
Recent Progress in Addressing RFI • RFI problem has been recognized over many years, and ESTO has supported technology development to make progress – Multiple IIP’s, ACT’s, and AITT 2002-2010 developed digital backends and algorithms for radiometry to detect and filter out RFI corrupted data – Project team members collaborated throughout these programs • Technology infused into SMAP’s L-band radiometer digital backend currently operating successfully in space – Project team members designed, developed, tested, and validated SMAP digital backend • RFI problem is even more challenging for future radiometer systems SMAP Future Number of bands 1 6 or more Bandwidth 20 MHz 100’s of MHz in each channel RFI Processing Yes Not possible (downlink on ground? (limited downlink volume) volume too high) RFI Processing No; not necessary Yes; only way to address on-board spacecraft? RFI challenge for future systems 3
Spectrum Allocations 6-40 GHz • Secondary allocations of limited utility • Current missions are operating outside protected bands and experiencing RFI – As spectrum use increases, problem will become worse: future radiometry missions (SCLP, GPM follow on, …) may become impossible – Worst case is weak RFI that makes its way into science products 4
CubeRRT: CubeSat Radiometer Radio Frequency Interference Technology Validation PI: Joel T. Johnson, Ohio State University Objective • Demonstrate wideband radio frequency interference (RFI) mitigating backend technology for future spaceborne microwave radiometers operating 6 to 40 GHz • Crucial to maintain US national capability for spaceborne radiometry and associated science goals • Demonstrate successful real-time on-board RFI detection and mitigation in 1 GHz instantaneous bandwidth • Demonstrate reliable cubesat mission operations, include tuning to Earth Exploration Satellite Service (EESS) allocated bands Nominal CubeRRT Configuration RFI sources in Europe at 10.7 GHz in the 6 to 40 GHz region observed by GPM Microwave Imager Approach Key Milestones • Build upon heritage of airborne and spaceborne (SMAP) digital • Requirements definition and system design 03/16 backends for RFI mitigation in microwave radiometry • Instrument engineering model subsystem tests 10/16 • Apply existing RFI mitigation strategies onboard spacecraft; • Instrument engineering model integration and test 12/16 downlink additional RFI data for assessment of onboard • Instrument flight model subsystem tests 04/17 algorithm performance • Instrument flight model integration and test 06/17 • Integrate radiometer front end, digital backend, and wideband antenna systems into 6U CubeSat • Spacecraft integration and test 12/17 • CSLI launch from ISS into 400 km orbit; ~ 120-300 km Earth • CubeRRT launch readiness 01/18 footprint for RFI mitigation validation • On-orbit operations completion L+12 months • Operate for one year at 25% duty cycle to acquire adequate RFI data Co-Is/Partners: C. Chen, M. Andrews, OSU; S. Misra, S. Brown, J. Kocz, R. Jarnot, TRL in = 5 TRL out = 7 JPL; D. Bradley, P. Mohammed, J. Lucey, J. Piepmeier, GSFC 2/16 InVEST-15-0020
CubeRRT Mission Properties 6
CubeRRT Development Overview • Engineering Model (EM) development, integration, and testing – Year 1 activity – Concludes with CDR (early 2017) • Flight Model (FM) development, integration, and testing – Year 2 activity – Concludes with flight ready system ready for launch (end 2017) • Mission operations – Year 3 activity 7
CubeRRT Development Overview • Engineering Model (EM) development, integration, and testing – Year 1 activity – Concludes with CDR (early 2017) • Flight Model (FM) development, integration, and testing – Year 2 activity – Concludes with flight ready system ready for launch (end 2017) • Mission operations – Year 3 activity 8
CubeRRT Subsystems and Team • Ohio State University (OSU) lead for payload/spacecraft system integration and test procedures • CubeRRT payload consists of 3 subsystems: – Radiometer Front End (RFE) • Design, development, test by NASA Goddard Space Flight Center (GSFC) – RF Digital Backend (RDB) • Design, development, test by NASA Jet Propulsion Laboratory (JPL) – Antenna (ANT) • Design, development, test by OSU • CubeRRT spacecraft bus (SC) – Design, development, test by Blue Canyon Technologies (BCT) 9
RFE Block Diagram • Antenna/reference load selector switch • Couple noise source • Heterodyne receiver • Sub-harmonic Image Rejection Mixer • IF in ADC’s second Nyquist zone (1-2 GHz) • Control for PLO (amplitude, harmonic) • Control fir IF: U/LSB and ampllitue 10
Noise Temperature Analysis Tsys$(K) B$(MHz) tau$(s) NEDT$(K) 500 1000 0.1 0.05 1420 1400 K 1390 500 10 0.1 0.50 1360 500 10 1 0.16 1330 1300 1000 1000 0.1 0.10 1270 1240 1000 10 0.1 1.00 1210 1000 10 1 0.32 1180 1150 2000 1000 0.1 0.20 1120 1090 2000 10 0.1 2.00 Noise Temperature (K) 1060 2000 10 1 0.63 1030 1000 4000 1000 0.1 0.40 970 940 4000 10 0.1 4.00 910 4000 10 1 1.26 880 850 820 790 760 730 700 670 640 610 580 550 520 490 460 400 K 430 400 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 34 35 37 38 39 40 6 16 26 36 Frequency (GHz) RFE only. 1 dB of cable/antenna loss adds 200-400 K 11
Algorithm Summary • The design has the Combined Algorithm following variable parameters – – Number of highest Cross Frequency (128ch/ Narrowband signals resolution channels 100ms) – Integration time Kurtosis (128-32ch/100ms) Pulsed-type/low-level RFI – Kurtosis threshold – CF threshold – Windowing used for CF Combined Flags 100ms 128 ch Product to be integrated Channels combined 64 ch Iterative Kurtosis and Cross- Frequency Detection 32 ch Combined RFI flag 12
CubeRRT RDB Processor 13
Preliminary Antenna Design
Preliminary Antenna Design Simulated Antenna Performance NADIR LHCP Realized Gain Reflection Coefficient
On-Orbit Configuration Zenith XB1 Control Unit Added power isolation board Deployed instrument antennas UHF Ant (2) Nadir Main Instrument Panel
Payload Components (1) Local Oscillator/ Interm 3.15” -Available Freq Assy cavity depth (LOA) – GSFC 7.75”L x 4.25”W x 1.5”H Working envelope Primary Structure (BCT) These 2 units (the Radiometer Front End - RFE) will be Antenna (OSU) integrated 3.94”L x 3.25”W x 2.22”H on the main instrument panel Working envelope Microwave Assembly (MWA) – GSFC 3.5”L x 2.65”W x 2.6” H Working envelope
Payload Components (2) Radiometer Back End (RDB) – JPL 5.0”L x 3.9”W x 1.08”H Working envelope 2 PWBs stacked Antenna envelope Harness Routing areas
Volume and Mass Margins Item Size (U) Mass (kg) Allocation Estimate Margin* Allocation Estimate Margin Payload 0.5 0.38 24% 0.2 0.20 0% Antenna 1 1.06 -6% 1 1.13 -13% RFE 1 0.13 87% 0.4 0.20 100% RDB 2.5 1.57 59% 1.6 1.53 5% Total 2.00 - 9.00 - Spacecraft 6 3.57 41% 14 10.53 25% Observatory Total * Margin = (Allocation – Estimate)/Allocation 19
Conops • Plan to observe at 25% duty cycle to manage battery DoD for 31 W payload • Emphasize land observations since focus is on scenes containing RFI • Flexible table-driven tuning of frequency to increase RFI measurements – Developing list of known RFI sources from TRMM and JMR observations (nadiral) – Large spot size: ~ 10 seconds observation time per footprint • Mission simulation tool developed to plan weekly observation schedule – Algorithms for auto-planning activities under development 20
Conclusions • CubeRRT will validate RFI detection and mitigation technologies for future Earth observing microwave radiometers operating 6-40 GHz • CubeRRT preliminary design completed • EM development proceeding to payload integration and test in Dec 2016 21
Questions? 22
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